using System;

class Teste{
  static void Troca(ref string s, ref string t)
  {
    string tmp = s;
    s = t;
    t = tmp;
  }
  static void Main()
  {
    string a = "Passo", b = "Coelho";
    Console.WriteLine(a + b);
    Troca(ref a, ref b);
    Console.WriteLine(a + b);
  }
}